Various methods of planar or non-planar techniques of fabrication of bubble domain device structures are known in the prior art. U.S. Pat. No. 4,172,758 of R. F. Bailey et al describes one basic fabrication technique for producing a magnetic bubble domain device. The copending U.S. patent application, Ser. No. 242,078, filed Mar. 9, 1981, and assigned to the common assignee, describes a planar method of device fabrication using a glass deposited by either sputtering or evaporation as the spacer layer between metal layers of the device. The drawback of such a configuration is that the Permalloy film can never be deposited without having a sharp non-planar component due to the troughs created during the lift-off step.
There are also a number of non-planar fabrication techniques in which various layers of materials are placed sequentially upon the original substrate, the layers generally following the contours of the preceeding layers. The disadvantage with such non-planar techniques is that in a multi-level device structure or composite, certain regions such as crossover areas, corners, and the like are subject to failure modes such as cracks, discontinuities, or other defects. In addition, reduced device behavior results from the interaction between non-planar Permalloy films and the magnetic "bubble" domains.
The disadvantages associated with the known planar or non-planar fabrication techniques make them impractical for implementation in devices in which smaller and smaller device structures are utilized, making greater demands upon the fabrication techniques. Prior to their present invention there has not been a satisfactory method of fabrication of bubble domain device structures capable of supporting a high density of magnetic bubble domains on the device.